Support for Font Awesome duotone and any other Font Awesome Pro icons

[adamwinn]

Prerequisites

• [x ] I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• [x ] The issue still exists against the latest master branch of yii2-icons.
• [x ] This is not an usage question. I confirm having gone through and read the documentation and demos.
• [x ] This is not a general programming / coding question. (Those should be directed to the webtips Q & A forum).
• [ ] I have attempted to find the simplest possible steps to reproduce the issue.
• [ ] I have included a failing test as a pull request (Optional).

Steps to reproduce the issue

Include support for Font Awesome Duotone icons

Expected behavior and actual behavior

Add support for Icon::FAD

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.